U.S. patent application number 10/896938 was filed with the patent office on 2005-08-25 for recording disk drive capable of reducing vibration within enclosure.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Asao, Yasuyoshi, Koizumi, Yoshiaki, Minamisawa, Ritsuko, Miura, Yasuhiro, Miyajima, Keiichi.
Application Number | 20050185329 10/896938 |
Document ID | / |
Family ID | 34857990 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050185329 |
Kind Code |
A1 |
Miyajima, Keiichi ; et
al. |
August 25, 2005 |
Recording disk drive capable of reducing vibration within
enclosure
Abstract
A recording disk is mounted on a hub in a recording disk drive.
The hub is mounted on a rotation shaft. The lower end of the
rotation shaft is received on a thrust bearing. The packing is
interposed between the enclosure and the thrust bearing. The
packing serves to protect the inner space of the enclosure from
dust. When the rotation shaft, the hub, the thrust bearing, and the
like are assembled into the enclosure, an urging force is applied
on the upper end of the rotation shaft. The thrust bearing urges
the packing against the enclosure. Since the top surface of the hub
is set lower than the top end of the rotation shaft, the urging
force is reliably received on the rotation shaft. The alignment
cannot be deteriorated between the rotation shaft and the hub.
Inventors: |
Miyajima, Keiichi;
(Kawasaki, JP) ; Asao, Yasuyoshi; (Kawasaki,
JP) ; Koizumi, Yoshiaki; (Kawasaki, JP) ;
Minamisawa, Ritsuko; (Kawasaki, JP) ; Miura,
Yasuhiro; (Kawasaki, JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki
JP
|
Family ID: |
34857990 |
Appl. No.: |
10/896938 |
Filed: |
July 23, 2004 |
Current U.S.
Class: |
360/99.08 ;
360/99.12; G9B/33.024 |
Current CPC
Class: |
G11B 33/08 20130101;
G11B 17/0287 20130101 |
Class at
Publication: |
360/099.08 ;
360/099.12 |
International
Class: |
G11B 017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2004 |
JP |
2004-042860 |
Claims
What is claimed is:
1. A closed recording disk drive comprising: a rotation shaft; a
thrust bearing receiving a bottom end of the rotation shaft; a
radial fluid dynamic bearing supporting the rotation shaft for
relative rotation around a rotation axis; a hub attached to the
rotation shaft so as to receive a recording disk and defining a top
surface lower than a top end of the rotation shaft; an enclosure
designed to contain the rotation shaft, the thrust bearing, the
radial fluid dynamic bearing, the recording disk and the hub so as
to receive the thrust bearing; and a packing interposed between the
enclosure and the thrust bearing.
2. A clamp for a recording disk drive, comprising; a clamp body
attached to a tip end of a rotary body so as to hold a recording
disk on the rotary body; and an attachment hole formed in the clamp
body so as to receive insertion of the rotary body, wherein said
attachment hole defines: a small hole portion positioning the
rotary body relative to the clamp body; and a large hole portion
continuously connected to the small hole portion, said large hole
portion expanding from the small hole portion in a centrifugal
direction of the rotary body.
3. The clamp according to claim 2, wherein the small hole portion
is defined at one end of the attachment hole, and the large hole
portion is designed to extend from the small hole portion to the
other end of the attachment hole.
4. The clamp according to claim 2, wherein the large hole portion
forms a space of a truncated cone tapered toward the small hole
portion.
5. A recording disk drive comprising: a rotary body; a recording
disk attached to the rotary body; a clamp attached to a tip end of
the rotary body so as to hold the recording disk against a flange
formed in the rotary body; and an attachment hole formed in the
clamp so as to receive insertion of the rotary body, wherein said
attachment hole defines: a small hole portion positioning the
rotary body relative to the clamp; and a large hole portion
continuously connected to the small hole portion, said large hole
portion expanding from the small hole portion in a centrifugal
direction of the rotary body.
6. The recording disk drive according to claim 5, wherein the small
hole portion is defined at a position closer to the flange, and the
large hole portion is defined at a position remoter from the
flange, said large hole portion extending from the small hole
portion toward a top end of the attachment hole.
7. The recording disk drive according to claim 6, wherein the large
hole portion forms a space of a truncated cone tapered toward the
small hole portion.
8. A spacer mounted on a rotary body between recording disks in a
recording disk drive, said spacer defining: a small hole portion
designed to form a cylindrical space; and a large hole portion
designed to form a space of a truncated cone continuous with the
cylindrical space, said truncated cone having an axis common to the
cylindrical space and tapered toward the cylindrical space, wherein
a generatrix of the truncated cone intersects a generatrix of the
cylindrical space within a plane including a rotation axis by an
angle smaller than 45 degrees.
9. The spacer according to claim 8, wherein the angle is set
smaller than 30 degrees.
10. A spacer mounted on a rotary body between recording disks in a
recording disk drive, said spacer defining: a small hole portion
designed to form a cylindrical space; a first large hole portion
designed to form a space of a truncated cone continuous with one
end of the cylindrical space, said truncated cone having an axis
common to the cylindrical space and tapered toward the cylindrical
space; and a second large hole portion designed to form a space of
a truncated cone continuous with the other end of the cylindrical
space, said truncated cone having an axis common to the cylindrical
space and tapered toward the cylindrical space, wherein a
generatrix of the truncated cones intersects a generatrix of the
cylindrical space within a plane including a rotation axis by an
angle smaller than 45 degrees.
11. The spacer according to claim 10, wherein the angle is set
smaller than 30 degrees.
12. A recording disk drive comprising; a rotary body; recording
disks mounted on the rotary body; and a spacer mounted on the
rotary body between the recording disks, wherein said spacer
defines: a small hole portion forming a cylindrical space; and a
large hole portion continuously connected to the small hole
portion, said large hole portion defining a space of a truncated
cone tapered toward the cylindrical space, wherein a generatrix of
the truncated cone intersects a generatrix of the cylindrical space
within a plane including a rotation axis by an angle smaller then
45 degrees.
13. A recording disk drive comprising: a rotary body; recording
disks mounted on the rotary body; and a spacer mounted on the
rotary body between the recording disks, wherein said spacer
defines: a small hole portion forming a cylindrical space; and
first and second large hole portions continuously connected to
opposite ends of the cylindrical space, said large hole portions
respectively defining a space of a truncated cone tapered toward
the cylindrical space, wherein a generatrix of the truncated cone
intersects a generatrix of the cylindrical space within a plane
including a rotation axis by an angle smaller than 45 degrees.
14. A spindle motor for a recording disk drive, comprising: a
rotor; a stator designed to support the rotor for relative
rotation; an electromagnet attached to the stator; and a depression
formed in the stator and designed to form a thinner portion.
15. A recording disk drive comprising: a recording disk; a rotor
designed to support the recording disk; a stator designed to
support the rotor for relative rotation; an electromagnet attached
to the stator; a depression formed in the stator and designed to
form a thinner portion; an enclosure receiving the stator; a head
actuator coupled to a support shaft standing from the enclosure for
relative rotation; and a head slider supported at a tip end of the
head actuator and opposed to a surface of the recording disk.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a clamp, a spacer and a
spindle motor utilized in a recording disk drive such as a hard
disk drive (HDD), for example.
[0003] 2. Description of the Prior Art
[0004] A spindle motor is assembled within an enclosure of a hard
disk drive (HDD), for example. The spindle motor includes a rotor
supported in a stator for relative rotation. A hard disk (HD), a
spacer and a clamp are mounted on the rotor. The stator is received
on the bottom plate of the enclosure. Ahead actuator is mounted on
the enclosure for swinging movement. A head slider is supported at
the tip or front end of the head actuator.
[0005] Electromagnets are attached to the stator for inducing
rotation of the rotor. When electric current is supplied to the
electromagnets, the interaction between the electromagnets and
permanent magnets on the rotor causes the rotor and the hard disk
to rotate. The swinging movement of the head actuator serves to
position the head slider at a target recording track on the hard
disk during the rotation of the hard disk. An electromagnetic
transducer mounted on the head slider is designed to write a magnet
bit data on the hard disk.
[0006] The rotor should be prevented from suffering from deviation
of rotation for achieving a higher recording density on the hard
disk. If the deviation of rotation is suppressed, the head slider
can accurately be positioned at a target recording track with a
higher accuracy. In this case, the hard disk, the clamp and the
spacer should be positioned on the rotor with a high accuracy. The
center of gravity of the clamp and the spacer must be aligned at
the rotation axis of the rotor.
[0007] Electromagnetic vibration is transmitted from the
electromagnets to the stator when electric current is supplied to
the electromagnets. If the vibration frequency of the
electromagnetic vibration corresponds to the natural frequency of
the spindle motor, the spindle motor heavily vibrates. The
vibration is transmitted from the enclosure to the head actuator,
namely the head slider. The head slider cannot be positioned at a
target recording track.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the present invention to
provide a recording disk drive capable of relatively easily
suppressing deviation of rotation. It is accordingly another object
of the present invention to provide a clamp and a spacer greatly
useful to realize the aforementioned recording disk drive. It is
accordingly another object of the present invention to provide a
spindle motor capable of relatively easily suppressing vibration in
a recording disk drive.
[0009] According to a first aspect of the present invention, there
is provided a closed recording disk drive comprising: a rotation
shaft; a thrust bearing receiving the bottom end of the rotation
shaft; a radial fluid dynamic bearing supporting the rotation shaft
for relative rotation around the rotation axis; a hub attached to
the rotation shaft so as to receive a recording disk and defining
the top surface lower than the top end of the rotation shaft; an
enclosure designed to contain the rotation shaft, the thrust
bearing, the radial fluid dynamic bearing, the recording disk and
the hub so as to receive the thrust bearing; and a packing
interposed between the enclosure and the thrust bearing.
[0010] The packing is interposed between the enclosure and the
thrust bearing in the recording disk drive. The packing seals the
inner space of the enclosure. The packing serves to protect the
inner space of the enclosure from dust. When the rotation shaft,
the hub, the thrust bearing and the radial fluid dynamic bearing
are assembled into the enclosure, the packing is urged between the
thrust bearing and the enclosure. An urging force is applied on the
upper end of the rotation shaft. The urging force is transmitted to
the thrust bearing from the lower end of the rotation shaft. The
thrust bearing urges the packing against the enclosure. Since the
top surface of the hub is set lower than the top or upper end of
the rotation shaft, the urging force is reliably received on the
rotation shaft. The alignment cannot be deteriorated between the
rotation shaft and the hub. In general, the upper end of the
rotation shaft is set lower than the level of the top surface of
the hub in a conventional recording disk drive. When the rotation
shaft, the hub, the thrust bearing and the radial fluid dynamic
bearing are assembled into the enclosure, the urging force is
received on the hub in the conventional recording disk drive. The
alignment cannot sufficiently be maintained between the rotation
shaft and the hub.
[0011] According to a second aspect of the present invention, there
is provided a clamp for a recording disk drive, comprising; a clamp
body attached to the tip end of a rotary body so as to hold a
recording disk on the rotary body; and an attachment hole formed in
the clamp body so as to receive insertion of the rotary body. In
this case, the attachment hole defines: a small hole portion
positioning the rotary body relative to the clamp body; and a large
hole portion continuously connected to the small hole portion, said
large hole portion expanding from the small hole portion in the
centrifugal direction of the rotary body.
[0012] When the clamp is mounted on the rotary body, the rotary
body is received in the small hole portion. The small hole portion
serves to position the rotary body relative to the clamp. If an
urging force is applied to the clamp on the rotary body based on
fastening means such as screws, for example, the clamp body gets
closer to the rotary body as the screws advance into the rotary
body. The clamp body bends upward at the outer periphery. This
causes the inner surface of the large hole portion to get closer to
the outer surface of the rotary body. Since the large hole portion
expands in the centrifugal direction of the rotary body, a
sufficient clearance can be established between the inner surface
of the large hole portion and the outer surface of the rotary body.
Deformation of the clamp body is accordingly accepted. The
fastening force can reliably be applied to the clamp body. The
clamp is allowed to hold the recording disk on the rotary body with
a clamping force as designed.
[0013] It is required to suppress deviation of rotation of the
rotary body for establishment of a higher recording density. The
clamp should be mounted on the rotary body with a higher positional
accuracy. The clamp according to the invention allows the inner
surface of the small hole portion to closely contact the rotary
body. The clamp can thus be positioned relative to the rotary body
at a higher accuracy. The center of gravity of the clamp can
reliably be aligned with the rotation axis of the rotation body.
Deviation of rotation of the rotary body can be suppressed to the
uttermost.
[0014] In a conventional clamp, an attachment hole forms a
cylindrical space. The inner surface of the attachment hole
contacts the outer surface of the rotary body. If an urging force
is applied to the clamp on the rotary body based on screws, for
example, the clamp body gets closer to the rotary body as the
screws advance into the rotary body. The clamp body bends upward at
the outer periphery. However, since the inner surface of the
attachment hole tightly contacts the outer surface of the rotary
body, deformation of the clamp body is inhibited. The screws cannot
tightly be screwed into the rotary body. The center of gravity of
the clamp should be displaced from the rotation axis of the rotary
body. The recording density of the magnetic recording disks cannot
be improved.
[0015] The small hole portion may be defined at one end of the
attachment hole, while the large hole portion is designed to extend
from the small hole portion to the other end of the attachment
hole. The large hole portion may form a space of a truncated cone
tapered toward the small hole portion.
[0016] The clamp is usually assembled in a recording disk drive.
The recording disk drive may thus include: a rotary body; a
recording disk attached to the rotary body; a clamp attached to the
tip end of the rotary body so as to hold the recording disk against
a flange formed in the rotary body; and an attachment hole formed
in the clamp so as to receive insertion of the rotary body. In this
case, the attachment hole should define: a small hole portion
positioning the rotary body relative to the clamp; and a large hole
portion continuously connected to the small hole portion, said
large hole portion expanding from the small hole portion in a
centrifugal direction of the rotary body. The small hole portion
may be defined at a position closer to the flange. The large hole
portion may be defined at a position remoter from the flange. The
large hole portion may extend from the small hole portion toward
the top end of the attachment hole.
[0017] According to a third aspect of the present invention, there
is provided a spacer mounted on a rotary body between recording
disks in a recording disk drive, said spacer defining: a small hole
portion designed to form a cylindrical space; and a large hole
portion designed to form a space of a truncated cone continuous
with the cylindrical space, said truncated cone having the axis
common to the cylindrical space and tapered toward the cylindrical
space, wherein the generatrix of the truncated cone intersects the
generatrix of the cylindrical space within a plane including the
rotation axis by an angle smaller than 45 degrees.
[0018] When the spacer is mounted on the rotary body, the large
hole portion receives insertion of the rotary body. Since the large
hole portion expands most at the opening, the rotary body is
allowed to easily get into the large hole portion. Moreover, since
the generatrix of the truncated cone intersects the generatrix of
the cylindrical space within a plane including the rotation axis by
an angle smaller than 45 degrees, the rotary body is smoothly
guided toward the small hole portion. Thereafter, the tip end of
the rotary body reaches the small hole portion. The tolerance is
set extremely small between the inner surface of the small hole
portion and the outer periphery of the rotary body, the spacer can
be positioned relative to the rotary body with a higher accuracy.
The center of gravity of the spacer can reliably be aligned with
the rotation axis of the rotary body. Deviation of rotation of the
rotary body can accordingly be suppressed to the uttermost. The
aforementioned angle may be set smaller than 30 degrees.
[0019] As describe above, it is required to suppress deviation of
rotation for establishment of a higher recording density. The
spacer should be mounted on the rotary body with a higher
positional accuracy. A higher recording density requires a reduced
tolerance between the inner surface of the small hole portion and
the outer periphery of the rotary body. In a conventional spacer,
an attachment hole forms a cylindrical space beveled at the
openings. Thin spaces of a truncated cone are defined at the
openings of the cylindrical space to get tapered toward the
cylindrical space. However, the generatrix of the individual
truncated cone is designed to intersect the generatrix of the
cylindrical space by an angle exactly equal to 45 degrees in the
conventional spacer. When the tip end of the rotary body collides
against the inner surface of the space of the truncated cone, the
tip end of the rotary body is hardly inserted into the cylindrical
space. It is more difficult to insert the rotary body into the
spacer of the conventional type if tolerance gets smaller between
the inner surface of the attachment hole and the outer periphery of
the rotary body. The assembling operation suffers from less
efficiency when the spacer is to be mounted on the rotary body.
[0020] The spacer may define: a small hole portion designed to form
a cylindrical space; a first large hole portion designed to form a
space of a truncated cone continuous with one end of the
cylindrical space, said truncated cone having the axis common to
the cylindrical space and tapered toward the cylindrical space; and
a second large hole portion designed to form a space of a truncated
cone continuous with the other end of the cylindrical space, said
truncated cone having the axis common to the cylindrical space and
tapered toward the cylindrical space.
[0021] The spacer of the aforementioned types may be assembled into
a recording disk drive. In this case, the recording disk drive may
include: rotary body; and recording disks mounted on the rotary
body. The spacer may be mounted on the rotary body between the
recording disks. The spacer may define: a small hole portion
forming a cylindrical space; and a large hole portion continuously
connected to the small hole portion, said large hole portion
defining a space of a truncated cone tapered toward the cylindrical
space. Additionally, the generatrix of the truncated cone
intersects the generatrix of the cylindrical space within a plane
including the rotation axis by an angle smaller then 45 degrees.
Likewise, the recording disk drive may include: rotary body; and
recording disks mounted on the rotary body. The spacer may be
mounted on the rotary body between the recording disks. The spacer
may define: a small hole portion forming a cylindrical space; and
first and second large hole portions continuously connected to
opposite ends of the cylindrical space, said large hole portions
respectively defining a space of a truncated cone tapered toward
the cylindrical space. Additionally, the generatrix of the
truncated cone intersects the generatrix of the cylindrical space
within a plane including the rotation axis by an angle smaller than
45 degrees.
[0022] According to a fourth aspect of the present invention, there
is provided a spindle motor for a recording disk drive, comprising:
a rotor; a stator designed to support the rotor for relative
rotation; an electromagnet attached to the stator; and a depression
formed in the stator and designed to form a thinner portion.
[0023] When electric current is supplied to the electromagnet,
electromagnetic vibration is transmitted to the stator from the
electromagnet. If the frequency of the vibration corresponds to the
natural frequency of any component of the stator, the vibration of
the stator is amplified. The spindle motor according to the
invention enables reduction in the rigidity of the stator based on
the thinner portion. In general, the frequency of the vibration
depends on the rigidity. If the depression is properly designed,
the natural frequency of the stator can be kept away from the
frequency of the electromagnetic vibration. The increase of the
vibration can be suppressed to the uttermost in the stator.
[0024] The spindle motor of the type may be assembled into a
recording disk drive. In this case, the recording disk drive may
include: a recording disk; a rotor designed to support the
recording disk; a stator designed to support the rotor for relative
rotation; an electromagnet attached to the stator; a depression
formed in the stator and designed to form a thinner portion; an
enclosure receiving the stator; a head actuator coupled to a
support shaft standing from the enclosure for relative rotation;
and a head slider supported at the tip end of the head actuator and
opposed to the surface of the recording disk.
[0025] The recording disk drive enables reduction in the rigidity
of the stator based on the thinner portion as described above. The
natural frequency of the stator can be kept away from the frequency
of the electromagnetic vibration. The increase of the vibration can
be suppressed to the uttermost in the stator. The head actuator is
prevented from receiving the vibration from the enclosure. The head
slider can be prevented from vibration in the head actuator. This
contributes to establishment of a higher recording density.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The above and other objects, features and advantages of the
present invention will become apparent from the following
description of the preferred embodiments in conjunction with the
accompanying drawings, wherein:
[0027] FIG. 1 is a plan view schematically illustrating the inner
structure of a hard disk drive (HDD) as a specific example of a
recording disk drive;
[0028] FIG. 2 is an enlarged sectional view, taken along the line
2-2 in FIG. 1, for schematically illustrating the structure of a
spindle motor according to a first example of the present
invention;
[0029] FIG. 3 is an enlarged partial sectional view of the spindle
motor for schematically illustrating the structure of a clamp;
[0030] FIG. 4 is an enlarged partial sectional view of the spindle
motor for schematically illustrating the structure of an annular
spacer;
[0031] FIG. 5 is an enlarged sectional view of the spindle motor
for schematically illustrating the annular spacer when the annular
spacer is to be mounted on a spindle hub;
[0032] FIG. 6 is an enlarged sectional view of the spindle motor
for schematically illustrating the clamp when the clamp is to be
mounted on the spindle hub;
[0033] FIG. 7 is an enlarged sectional view of the HDD for
schematically illustrating the spindle motor when the spindle motor
is to be mounted on an enclosure of the HDD;
[0034] FIG. 8 is an enlarged sectional view, corresponding to FIG.
2, for schematically illustrating the structure of a spindle motor
according to a second embodiment of the present invention; and
[0035] FIG. 9 is an enlarged sectional view, corresponding to FIG.
8, for schematically illustrating the structure of a spindle motor
according to a modification of the second embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] FIG. 1 schematically illustrates the inner structure of a
hard disk drive (HDD) 11 as an example of a recording disk drive or
storage device according to an embodiment of the present invention.
The HDD 11 includes a box-shaped main enclosure 12 defining an
inner space of a flat parallelepiped for example. At least one
magnetic recording disk 13 is mounted on the driving shaft of a
spindle motor 14 within the main enclosure 12. The spindle motor 14
is allowed to drive the magnetic recording disk 13 for rotation at
a higher revolution speed such as 7,200 rpm, 10,000 rpm, 15,000
rpm, or the like, for example. A cover, not shown, is coupled to
the main enclosure 12 so as to define the closed inner space
between the main enclosure 12 and the cover itself. A packing is
interposed between the main enclosure 12 and the cover.
[0037] A head actuator 15 is also accommodated in the inner space
of the main enclosure 12. The head actuator 15 comprises an
actuator block 16. The actuator block 16 is coupled to a vertical
support shaft 17 standing from the bottom plate of the main
enclosure 12 for relative rotation. Rigid actuator arms 18 are
defined in the actuator block 16 so as to extend in the horizontal
direction from the vertical support shaft 17. The actuator arms 18
are related to the front and back surfaces of the magnetic
recording disk 13. The actuator block 16 may be made of aluminum.
Molding process may be employed to form the actuator block 16.
[0038] Head suspensions 19 are fixed to the corresponding tip ends
of the actuator arms 18. The individual head suspension 19 extends
forward from the tip end of the actuator arm 18. A flying head
slider 21 is supported on the front end of the head suspension 19.
The flying head sliders 21 are in this manner connected to the
actuator block 16. The flying head sliders 21 are opposed to the
surfaces of the magnetic recording disk or disks 13.
[0039] An electromagnetic transducer, not shown, is mounted on the
flying head slider 21. The electromagnetic transducer may include a
read element and a write element. The read element may include a
giant magnetoresistive (GMR) element or a tunnel-junction
magnetoresistive (TMR) element designed to discriminate magnetic
bit data on the magnetic recording disk 13 by utilizing variation
in the electric resistance of a spin valve film or a
tunnel-junction film, for example. The write element may include a
thin film magnetic head designed to write magnetic bit data into
the magnetic recording disk 13 by utilizing a magnetic field
induced at a thin film coil pattern.
[0040] The head suspension 19 serves to urge the flying head slider
21 toward the surface of the magnetic recording disk 13. When the
magnetic recording disk 13 rotates, the flying head slider 21 is
allowed to receive airflow generated along the rotating magnetic
recording disk 13. The airflow serves to generate a positive
pressure or lift on the flying head slider 21. The flying head
slider 21 is thus allowed to keep flying above the surface of the
magnetic recording disk 13 during the rotation of the magnetic
recording disk 13 at a higher stability established by the balance
between the urging force of the head suspension 19 and the
lift.
[0041] A power source 22 such as a voice coil motor (VCM) is
connected to the actuator block 17. The power source 22 is designed
to drive the actuator block 17 for rotation around the support
shaft 16. The rotation of the actuator block 17 induces the
swinging movement of the actuator arms 18 and the head suspensions
19. When the actuator arm 18 is driven to swing about the support
shaft 16 during the flight of the flying head slider 21, the flying
head slider 21 is allowed to cross the recording tracks defined on
the magnetic recording disk 13 in the radial direction of the
magnetic recording disk 13. This radial movement serves to position
the flying head slider 21 right above a target recording track on
the magnetic recording disk 13. As conventionally known, in the
case where two or more magnetic recording disks 13 are incorporated
within the inner space of the main enclosure 12, a pair of the
actuator arm 18 as well as a pair of the head suspension 19 is
disposed between the adjacent magnetic recording disks 13.
[0042] FIG. 2 illustrates the structure of the spindle motor 14
according to a first embodiment of the present invention. The
spindle motor 14 includes a stator 23 and a rotor 24. The rotor 24
is supported in the stator 23 for relative rotation. The stator 23
includes a bracket 25 received on the main enclosure 12. The
bracket 25 is received in a receiving hole 26 formed in the bottom
plate of the main enclosure 12. A cylindrical portion 25a is formed
on the bracket 25. The cylindrical portion 25a stands upright from
the upper surface of the basement of the bracket 25. The bracket 25
may be fixed with screws 27 on the main enclosure 12, for example.
The bracket 25 may be cut out of a mass of aluminum, or the
like.
[0043] A packing 28 is interposed between the bracket 25 and the
main enclosure 12. The packing 28 may take the form of an
annularity, for example. The packing 28 may be made of an elastic
resin material such as a rubber, for example. The packing 28 is
tightly contact the bracket 25 and the main enclosure 12. The
packing 28 serves to protect the main enclosure 12 from dust
passing through the receiving hole 26.
[0044] The stator 23 includes a sleeve 29 received in the
cylindrical portion 25a. First and second columnar spaces 31, 32
are defined within the sleeve 29. The second columnar space 32 is
formed continuous with the first columnar space 31. The diameter of
the second columnar space 32 is set larger than that of the first
columnar space 31. The sleeve 31 may be made from a metallic
material such as brass, stainless steel, or the like. A thrust
plate 33 is fitted in the lower opening of the sleeve 29. The
thrust plate 33 is designed to seal the lower opening of the sleeve
29.
[0045] The stator 23 includes stator cores 34 coupled to the outer
surface of the cylindrical portion 25a, and electromagnets or coils
35 wound around the stator cores 34. The individual stator core 34
comprises stacked metallic thin plates.
[0046] The rotor 24 includes a rotary body 36. The rotary body 36
includes a rotation shaft 37, and a spindle hub 38 fixed to the
rotation shaft 37. The rotation shaft 37 is received in the first
and second columnar spaces 31, 32. Fluid such as oil 39 is filled
between the rotation shaft 37 and the sleeve 29. The rotation shaft
37 is supported in the sleeve 29 in this manner. A disciform thrust
flange 41 is fixed to the rotation shaft 37. The thrust flange 41
is contained within the second cylindrical space 32. The upper
surface of the thrust plate 33 is opposed to the bottom surface of
the thrust flange 41. The rotation shaft 37 and the thrust flange
41 may be made from a metallic material such as brass, a stainless
steel, or the like.
[0047] A columnar inner space is defined within the spindle hub 38.
The stator 23 is contained within the inner space. The rotation
shaft 37 is tightly inserted into a through bore defined in the
upper surface of the spindle hub 38. An adhesive may be utilized to
fix the rotation shaft 37 to the spindle hub 38, for example. The
spindle hub 38 is in this manner connected to the bracket 25 for
relative rotation around the rotation axis 42 of the rotation shaft
37. The level of the upper surface of the spindle hub 38 is set
lower than that of the top end of the rotation shaft 37. In other
words, the rotation shaft 37 is designed to protrude from the upper
surface of the spindle hub 38.
[0048] The inner surface of the spindle hub 38 is opposed to the
outer cylindrical surface of the cylindrical portion 25a. A yoke 43
and permanent magnets 44 are fixed to the inner surface of the
spindle hub 38. The permanent magnets 44 are thus opposed to the
coils 35. When electric current is supplied to the coils 35, the
magnetic field generated at the coils 35 serves to induce the
rotation of the rotary body 36 or spindle hub 38 around the
rotation axis 42.
[0049] For example, four magnetic recording disks 13 are mounted on
the spindle hub 38. A through hole 13a is defined at the center of
the individual magnetic recording disk 13 so as to receive the
spindle hub 38. An annular spacer 45 is interposed between the
adjacent magnetic recording disks 13 around the spindle hub 38. The
annular spacers 45 serve to maintain a predetermined space between
the adjacent magnetic recording disks 13.
[0050] A flange 46 is formed on the spindle hub 38. The flange 46
extends outward from the lower end of the spindle hub 38. The
lowest magnetic recording disk 13 is received on the flange 46. A
clamp 47 is attached to the upper end of the spindle hub 38. The
clamp 47 includes a clamp body 47a. Four screws 48 are utilized to
fix the clamp body 47a to the spindle hub 38, for example. Through
bores 49 may be defined in the clamp body 47a so as to receive the
screws 48. An attachment hole 51 is defined in the clamp body 47a
so as to receive insertion of the spindle hub 38. Protrusions 47b
are defined in the clamp body 47a. The protrusions 47b are designed
to contact the surface of the uppermost magnetic recording disk 13.
The magnetic recording disks 13 and the annular spacers 45 are held
between the clamp 47 and the flange 46 in this manner.
[0051] As shown in FIG. 3, a small hole portion 52 is defined in
the attachment hole 51. The small hole portion 52 is designed to
position the spindle hub 38 relative to the clamp body 47a. The
small hole portion 47a forms a cylindrical space. The inner surface
of the small hole portion 52 contacts the outer cylindrical surface
of the spindle hub 38. The inner diameter of the small hole portion
52 corresponds to the minimum diameter of the attachment hole 51 in
the clamp body 47a. The attachment hole 51 defines the small hole
portion 52 at the end closer to the flange 46, namely at the lowest
end.
[0052] A large hole portion 53 is also defined in the attachment
hole 51. The large hole portion 52 is continuously connected to the
small hole portion 51. The large hole portion 53 expands from the
small hole portion 52 in the centrifugal direction of the spindle
hub 38. The large hole portion 53 extends from the small hole
portion 52 toward the other end or highest end of the attachment
hole 51. The large hole portion 53 forms a space of a truncated
cone tapered toward the small hole portion 52. The inner surface of
the large hole portion 53 keeps distanced from the outer surface of
the spindle hub 38 in this manner.
[0053] As shown in FIG. 4, a small hole portion 54 is defined in
the individual annular spacer 45. The small hole portion 54 forms a
cylindrical space. The inner surface of the small hole portion 54
contacts the outer cylindrical surface of the spindle hub 38. The
inner diameter of the small hole portion 54 corresponds to the
minimum inner diameter of the annular spacer 45. The small hole
portion 54 is designed to position the spindle hub 38 relative to
the annular spacer 45.
[0054] First and second large hole portions 55, 56 are defined in
the individual annular spacer 45. The first large hole portion 55
forms a space of a truncated cone continuously connected to one end
or the upper end of the cylindrical space. The truncated cone has
the axis common to the cylindrical space and tapered toward the
cylindrical space. The second large hole portion 56 also forms a
space of a truncated cone continuously connected to the other end
or lower end of the cylindrical space. The truncated cone likewise
has the axis common to the cylindrical space and tapered toward the
cylindrical space. The openings of the first and second large hole
portions 55, 56 establish the maximum inside diameter of the
annular spacer 45. The generatrices of the truncated cones are
designed to intersect the generatrix of the cylindrical space
within a plane including the rotation axis 42 by an angle .alpha.
smaller than 45 degrees. Here, the angle .alpha. may be set smaller
than 30 degrees. It should be noted that the first large hole
portion 55 may be omitted in the spacer 45.
[0055] Now, assume that the rotation shaft 37 starts rotating along
with the magnetic recording disks 13. When electric current is
supplied to the coils 35, a driving power is generated between the
coils 35 and the permanent magnets 44. When the rotation shaft 37
starts rotating, the oil 39 is allowed to flow along the inner
surface of the sleeve 29. The oil 39 serves to generate dynamic
pressure. The dynamic pressure establishes a predetermined constant
gap between the outer surface of the rotation shaft 37 and the
inner surface of the sleeve 29. The dynamic pressure also
establishes a predetermined constant gap between the bottom surface
of the thrust flange 41 and the upper surface of the thrust plate
33. The rotation axis of the rotation shaft 37 thus aligns with the
aforementioned rotation axis 42. The rotation shaft 37 along with
the magnetic recording disks 13 keeps smoothly rotating in this
manner. Here, the sleeve 29 and the oil 39 function as a radial
fluid dynamic bearing to the rotation axis 37. Likewise, the thrust
plate 33 or bracket 25 and the oil 39 function as a thrust fluid
dynamic bearing. The radial fluid dynamic bearing and the thrust
fluid dynamic bearing forms a fluid dynamic bearing apparatus. When
the coils 35 stops receiving the electric current, the driving
force to the rotation shaft 37 disappears. The rotation shaft 37
stops rotating along with the magnetic recording disks 13. The oil
39 stops flowing. The dynamic pressure disappears, so that the
lower end of the rotation shaft 37 is received on the upper surface
of the thrust plate 33.
[0056] Next, assume that the magnetic recording disks 13, the
annular spacers 45 and the clamp 47 are to be mounted on the
spindle motor 14. The first magnetic recording disk 13 is mounted
on the flange 46. The spindle hub 38 is received in the through
hole 13a of the recording disk 13. The annular spacer 45 is then
mounted on the spindle hub 38. As shown in FIG. 5, for example, the
spindle hub 38 is inserted into the second large hole portion 56 of
the annular spacer 45. The second large hole portion 56 provides
the maximum diameter at the opening, so that the spindle hub 38 is
allowed to easily get into the second large hole portion 56.
Moreover, the second large hole portion 56 has the aforementioned
angle .alpha. as described above, so that the spindle hub 38 is
smoothly guided toward the small hole portion 54. Thereafter, the
upper end of the spindle hub 38 reaches the small hole portion 54.
Since the tolerance is set extremely small between the inner
diameter of the small hole portion 54 and the outer diameter of the
spindle hub 38, the annular spacer 45 can be positioned relative to
the spindle hub 38 with a higher accuracy. The center of gravity of
the annular spacer 45 can reliably be aligned with the rotation
axis 42. Deviation of rotation of the spindle motor 14 can
accordingly be suppressed to the uttermost. Afterward, the magnetic
recording disks 13 and the annular spacers 45 are alternately
mounted on the spindle hub 38.
[0057] It is required to suppress deviation of rotation for
establishment of a higher recording density. The annular spacers 45
must be mounted on the spindle hub 38 with a higher positional
accuracy. A higher recording density requires a reduced tolerance
between the inner diameter of the small hole portion 54 and the
outer diameter of the spindle hub 38. In a conventional annular
spacer, an attachment hole forms a cylindrical space beveled at the
openings. Thin spaces of a truncated cone are defined at the
openings of the cylindrical space to get tapered toward the
cylindrical space. However, the generatrix of the individual
truncated cone is designed to intersect the generatrix of the
cylindrical space by an angle exactly equal to 45 degrees. When the
upper end of the spindle hub collides against the inner surface of
the space of the truncated cone, the upper end of the spindle hub
is hardly inserted into the cylindrical space. It is more difficult
to insert the spindle hub into the annular spacer of the type if
tolerance gets smaller between the inner diameter of the attachment
hole and the outer diameter of the spindle hub. The assembling
operation suffers from less efficiency when the annular spacer is
to be mounted on the spindle hub.
[0058] After the uppermost recording disk 13 is mounted on the
spindle hub 38, the clamp 47 is mounted on the spindle hub 38. The
spindle hub 38 is received into the small hole portion 52 of the
attachment hole 51. The small hole portion 52 positions the spindle
hub 38 relative to the clamp 47. The through bores 49 of the clamp
body 47a may previously be positioned at the screw holes 57 defined
in the spindle hub 38. The screws 48 are then inserted through the
through bores 49 and thereafter screwed into the screw holes 57 at
a regular fastening torque. As shown in FIG. 6, for example, the
protrusions 47b contact the surface of the uppermost magnetic
recording disk 13. When the screws 48 are further screwed into the
screw holes 57, the clamp body 47a gets closer to a step 38a of the
spindle hub 38. The clamp body 47a bends upward at the outer
periphery. This causes the inner surface of the large hole portion
53 to get closer to the outer surface of the spindle hub 38. Since
the large hole portion 53 forms a space of a truncated cone as
described above, a sufficient clearance can be established between
the large hole portion 53 and the spindle hub 38. The deformation
of the clamp body 47a is acceptable. The fastening force of the
screws 48 can reliably be applied to the clamp body 47a. The
protrusions 47b are allowed to hold the magnetic recording disks 13
at a clamping force as designed. In addition, the inner surface of
the small hole portion 52 reliably contacts the outer surface of
the spindle hub 38, so that the clamp 47 can be positioned at the
spindle hub 38 at a higher accuracy. The center of gravity of the
clamp 47 can reliably be aligned with the rotation axis 42.
Deviation of rotation of the spindle motor 14 can be suppressed to
the uttermost. Furthermore, the deformation of the clamp body 47a
is acceptable, so that the screws 47 and the through bores 49 are
prevented from receiving an abnormal load.
[0059] In a conventional clamp, an attachment hole forms a
cylindrical space. The inner surface of the attachment hole
contacts the outer surface of the spindle hub. When screws are
screwed into the spindle hub, protrusions are forced to contact the
uppermost magnetic recording disk in the same manner as described
above. However, since the inner surface of the attachment hole
tightly contacts the outer surface of the spindle hub, deformation
of the clamp body is inhibited. The screws cannot further be
screwed anymore. The center of gravity of the clamp should be
displaced from the rotation axis of the spindle hub. The recording
density of the magnetic recording disks cannot be improved.
Moreover, not only a clamping force cannot be obtained as designed,
but also the screws and the screw holes suffer from an abnormal
load.
[0060] As shown in FIG. 7, for example, the spindle motor 14 is
then assembled into the main enclosure 12. The packing 28 is
previously attached to the bracket 25. When the spindle motor 14 is
received in the receiving hole 26, the packing 28 is interposed
between the bottom surface of the bracket 25 and a step 26a of the
receiving hole 26. An urging member 58 is employed to apply the
urging force at the upper end of the rotation shaft 37. The urging
force is transmitted from the bottom end of the rotation shaft 37
to the thrust plate 33, namely the bracket 25. The bracket 25 urges
the packing 28 against the step 26a. When the bottom surface of the
bracket 25 has been received on the step 26a, the screws 27 is
inserted into the main enclosure 12. The spindle motor 14 is thus
fixed to the main enclosure 12 in this manner.
[0061] The upper surface of the spindle hub 38 is set lower than
the top end of the rotation shaft 37 in the aforementioned HDD 11.
The urging force is reliably received on the rotation shaft 37. The
alignment cannot be deteriorated between the rotation shaft 37 and
the spindle hub 38. On the other hand, the top end of the rotation
shaft is set lower than the upper surface of the spindle hub in a
conventional HDD. The urging force is received on the upper surface
of the spindle hub when the spindle motor is assembled into the
HDD. The alignment cannot sufficiently be maintained between the
rotation shaft and the spindle hub.
[0062] FIG. 8 illustrates the structure of the spindle motor 14a
according to a second embodiment of the present invention. A
depression 61 is defined in the bracket 25 in the spindle motor
14a. Here, the depression 61 is located on the bracket 25 outside
the cylindrical portion 25a. The depression 61 is designed to
extend in the circumferential direction of the cylindrical portion
25a, for example. The depression 61 may be an elongated groove
extending in the circumferential direction of the cylindrical
portion 25a. Alternatively, depressions 61 may be arranged in a row
in the circumferential direction of the cylindrical portion 25a.
The depression 61 serves to form a thinner portion 62 in the
bracket 25. The rigidity of the bracket 25 is decreased at the area
of the thinner portion 62. Like reference numerals are attached to
components or structures equivalent to those of the aforementioned
first embodiment.
[0063] When electric current is supplied to the coils 35,
electromagnetic vibration induced in the coils 35 is transmitted to
the bracket 25. If the frequency of the electromagnetic vibration
corresponds to the natural frequency of the bracket 25, the
vibration of the bracket 25 is greatly enhanced. The vibration is
then transmitted to the head actuator 15 through the bottom plate
of the main enclosure 12. The head slider 21 vibrates in the head
actuator 15. A reduced vibration contributes to a higher recording
density.
[0064] The thinner portion 62 based on the depression 61 serve to
decrease the rigidity of the bracket 25. Generally, the frequency
of vibration depends on the rigidity. If the depression 61 is
properly designed, the natural frequency of the bracket 25 can be
kept away from the frequency of the electromagnetic vibration. The
increase of vibration can be suppressed to the uttermost in the
bracket 25. The head slider 21 can reliably be prevented from
receiving transmission of vibration.
[0065] In a conventional spindle motor, the frequency of the
electromagnetic vibration is shifted by changing design such as
means for supporting the cores, condition for magnetizing the
coils, structure of the bearing apparatus. Operations such as
redesign, experiment, and examination are repeated. It takes a long
time to accomplishing the design of products. On the other hand,
according to the spindle motor 14a of the present invention, the
depression 61 serves to suppress the vibration in a facilitated
manner.
[0066] The vibration of the spindle motor 14a is measured for
deciding the arrangement and size of the depression 61. A
vibroscope is attached to the spindle motor 14a. The vibration of
the bracket 25 is measured based on the vibroscope. The position
and extent of the depression 61 are determined based on the
measurement. A drill may be employed to form the depression 61.
[0067] In addition, as shown in FIG. 9, the depression 61 may be
formed in the cylindrical portion 25a of the bracket 25, for
example. Otherwise, the depression 61 may be formed in the other
area of the bracket 25. Like reference numerals are attached to
components or structures equivalent to those of the aforementioned
first and second embodiments.
[0068] A ball bearing apparatus or a rolling bearing apparatus, or
the other types of a bearing apparatus may be employed in the
aforementioned spindle motor 14, 14a, 14b, in addition to the
aforementioned fluid dynamic bearing apparatus.
* * * * *